Two-system moisture applicator for a lithographic press

ABSTRACT

A two-system moisture applicator for masters on a lithographic press. The first system rotates to contact the master, and is retracted by lowering its pivot center to cause a cam and follower to move the system away. The other system is conventional.

United States Patent 2,798,426 7/1957 Janke etal.

Inventors Arthur W. Sejedt Kirkland; Ronald J. Garcowski, Cleveland, both of, Ohio Appl. No. 786,651

Filed Dec. 24, 1968 Patented SepL 14, 1971 Assignee Addrmograph Multigraph Corporation Cleveland, Ohio TWO-SYSTEM MOISTURE APPLICATOR FOR A LITHOGRAPHIC PRESS 6 Claims, 11 Drawing Figs.

US. Cl 101/148, 101/351 Int. CL B411 7/40 FieldolSearch 101/132.5, 147,148, 351, 352,144

RefereneesCited UNlTED STATES PATENTS 3,056,346 10/1962 Gammeter et a1. 101/144 3,259,062 7/1966 101/148 X 3,304,863 2/1967 101/351 3,411,442 11/1968 101/148 3,412,676 11/1968 101/148X 3,425,345 2/1969 101/148 3,431,841 3/1969 101/148X 3,451,336 6/1969 101/132.5 3,280,733 10/1966 101/147 FOREIGN PATENTS 1,279,690 10/1968 Germany 101/148 Primary Examiner-Robert E Pulfrey Assistant Examiner.l. Reed Fisher AttorneysRussell L. Root and Ray S. Pyle ABSTRACT: A two-system moisture applicator for masters on a lithographic press. The first system rotates to contact the master, and is retracted by lowering its pivot center to cause a cam and follower to move the system away. The other system is conventional.

PATENTED SEPI 41911 sum 2 or 3 ARTHUR I4. Sf/ECK RONALD d. GARC OWSK/ B N VE PATENIED SEP] 4197:

SHEEI 3 BF 3 ARTHUR W SE/E CK RONALD J. GARCOWSK/ IN VEN '7 'O/ 1;

BYfa 5 TWO-SYSTEM MOISTURE APPLICATOR FOR A LITHOGRAPHIC PRESS BACKGROUND OF THE INVENTION A lithographic printing plate, whether it be stone, metal or paper, must present a background which rejects ink, and an image which accepts ink. In modern office procedures, paper masters are becoming predominant. Regardless of what type of master is being employed, the background area must be prepared to reject the ink and accept moisture. Background preparation is a chemical conversion. Thereafter, the moisture used in the printing cycle, although a chemical solution, serves the primary purpose of supplying ink rejecting moisture.

The original procedure in preparation of a master was to convert the surface by hand rubbing with a solution soaked pad while the master lay flat on a support surface. Then, after the master was installed upon the master cylinder of the machine, rollers kept a constant supply of wetting solution applied to the master surface in order that the background would be moist and the moisture in the background would cause the ink from an ink roller to be rejected.

In order to expedite the preparation of masters, U.S. Pat. No. 2,443,458 has taught a means for placing a dry master on the master cylinder and applying the conversion and preparation liquid while on the master cylinder. Operators skill determined the length of time that a saturated sponge was held against the surface of the master, except for some versions of these machines which have counting devices for producing a counted number of revolutions before the application is stopped.

In the logical development of lithography for office procedures, preprepared masters are stock-piled for the preparation of limited supplies of regularly required forms and similar printed matter. A stack of such preprepared dry masters is placed in mechanical installation devices, which installs the masters on the master cylinder in a dry condition and ejects the master after a counted number of prints have been made from the master.

The present invention has freed the operator from the necessity of attending the machine for the purpose of applying the preliminary conversion and preparation solution after the master is mechanically installed.

SUMMARY OF INVENTION In a lithographic printing press having a master cylinder, and with means for installing dry preprepared masters one-byone, an applicator scrubs the surface of the dry master on the cylinder with a preparation liquid for an interval of time determined by a timing circuit according to the requirements of master surface preparation.

After the master is installed dry, and then wetted with the preparatory solution for the required time, the preparation apparatus is moved to an inoperative condition and a fountain solution roller series is brought against the surface of the master to supply repellent fountain solution during the actual printing cycle.

The objects achieved by the invention will become more apparent as the preferred embodiment of the invention is illustrated and described hereafter.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of an embodiment of the invention, showing only the moisture roller systems in phantom outline through the side plate of the frame;

FIG. 2, on pg. 2 of the drawings, is a perspective view, with some parts in exploded relationship, of a subframe with one moisture roller system held therein;

FIG. 3 is an end elevation of the subframe and rollers of FIG. 2, with a roller retention structure added, and the holding and camming parts of FIG. 2 removed;

FIG. 4 is a front elevation, of one end of the roller system, illustrating the roller retention structure of FIG. 3;

FIG. 5 is a diagrammatic arrangement of drive transmission gears located on the end opposite FIG. 3, shown in exploded relationship in FIG. 2;

FIG. 6 is a section taken along lines 6-6 of FIG. 5;

FIG. 7 on page 1 of the drawings is a side illustration, to an enlarged scale, of the moisture system containing the subframe of FIG. 3, with the electrically powered drive system restored, which was omitted from FIG. 1;

FIGS. 8 and 9 are schematic illustrations of the moisture systems movements during their operative cycle;

FIG. 10 is an electrical diagram of that portion of the control system directly in control of the moisture system; and

FIG. 11 represents the control system for the entire machine, including a variable resistor of FIG. 10.

DESCRIPTION OF PREFERRED EMBODIMENT The principles of this invention may be applied to substantially any lithographic printing device having a rotary master holding cylinder. For this reason, the drawings have been restricted to illustrating only the dual moisture applicating system of the invention. A portion of a frame 10 is illustrated to represent a lithographic machine of any design or construction which may be desired. The illustrated preferred embodiment is in actual commercial use on an Addressograph-Multigraph 1250 lithographic press. The word "Multilith and the number designation I250 are trademarks of the Addressograph-Multigraph Corporation, Cleveland, Ohio, USA.

A master cylinder 11 of conventional construction is represented by a circular end view in FIG. 1. A frame 13, which consists of laterally spaced, rigid iron castings crossed braced, provides support for all of the moisture application rolls and fountains of this invention.

A substantially conventional fountain solution system is provided by a series of rollers culminating in a moisture form roll 14. The series begins at a fountain l5 supplied by a storage bottle and tube, which has not been illustrated in the drawings. This type of fountain solution roll system is conventional and known. It provides the constant supply of moisture needed to keep the background of a master oleophobic. As printing progresses, the sheets of paper will pick up the moisture from the master and this moisture must be constantly replaced in order to prevent ink from depositing in the background.

The frame 13 is pivoted about a pivot rod 17 in order that the moisture form roll 14 may be caused to move into contact with the surface of a master on the cylinder 11, or withdrawn therefrom between printing cycles.

Frame 13 is held poised above cylinder 11 by springs, and must be forced down to bring the moisture rollers into contact with the master cylinder. A lever arm 19, carried by frame 13, is used as the drive arm to cause the frame 13 to pivot about pivot 17. A cam follower 20 carried by the arm 19 is driven by a rotary cam 21. Cam 21 is oscillated between the illustrated position wherein the frame 13 is elevated, and a position wherein the high peak of the cam 21 is against the follower 20. Contact of the cam high area with follower 20 will force the frame down, to bring roller 14 in contact with the cylinder surface.

The cam 21 is manually operable by means of a drive handle 22, but is connected through conventional power systems to be driven in proper sequence from a timing control system. The operator is able ut use the handle 22 to test and adjust the apparatus, but during the production use of the equipment, the oscillation of cam 21 is accomplished by electronic control means operating through drive devices.

The electrical control means and conventional drive devices are eliminated from the drawings, these systems being known devices well within the knowledge of the lithographic design and maintenance engineer. However, a schematic diagram is provided in FIG. 10 to indicate the use of a variable capacitor circuit used to start and end the prewetting cycle.

The purpose of this invention is to enable the insertion and printing from a plurality of dry masters by mechanical installation devices, without operator attendance. Prior devices require an operator to install one dry master and then force a sponge against the surface of that master as it rotates on the cylinder. The sponge is saturated with the required prewetting and conversion solution necessary to prepare the master for use. The operator is required to be in attendance at installation of every master. This invention provides a device to take over that operation whenever a loader device is used to install the masters in a sequence without operator attention,

There are many and varied mechanical loading devices for installing masters on master cylinders of duplicating machines. One example is the Gam meter US Pat. No. 3,420,169 issued .Ian. 7, I969. The Gammeter patent illustrates the installation of a master that is preconverted and therefore wet, although that device will work very well on dry masters. Because the art of mechanical installation is so very old and well known, it is believed that no further illustration or teaching is necessary for instructing those skilled in the art.

A subframe 29, shown separated from the frame 13 in the FIGS. 2 through 6, carries a series of moisture rollers. Subframe 29 is supported on frame 13 by a pivot shaft 31, which also serves as a source of driving power. The subframe has two lateral side plates 30 upon which the rollers are supported.

The subframe 29 supports a form roller 33 which actually contacts the surface of the master on cylinder 11. A downwardly opening slot 34 in side plate 30 permits the axis shaft of roller 33 to move relative to the subframe.

An intermediate roller 36 is mounted in plastic bushings which are fixed in side plates 30. A third roll, designated an acceptor roll and indicated by the character reference 39, is mounted in an upwardly opening slot 40 of the side plates. The roll 39 is named an acceptor to designate the fact that it accepts the moisture which is transmitted through the train series of rollers to the form roller 33.

The form roller 33 is positioned in the slot 34 without direct retention by the side plate 30. A hook 42, as seen best in FIGS. 3 and 4, extends down to the shaft of roller 33 and holds it within slot 34. Slots 37 in the hooks allow the hooks to span the shaft of roller 36 and to move relative to the plates 30.

The roller 39 sits in the top position with its shaft projecting into the slot 40 without direct retention by the subframe 30. A clip 43 caps over the slot 40 and retains the roller 39.

A spring 44 interconnects the hook 42 and the clip 43 by connection posts, as best seen in FIG. 4. The upward thrust thus produced on roller 33, and the downward thrust upon the roller 39 causes the two rollers to press together against the roller 36.

The subframe 29 is shown in a vertical position in FIG. 3. Its operative position is suggested in the perspective FIG. 2, but shown more accurately in FIG. 1. A hook 46 is mounted on the main frame by guide members which fit through the two holes seen in the hook 46, best shown in FIG. 2. The vertical position of the hook is then established by the thumb screw at its top end. The hook fits under the shaft extension of the intermediate roller 36 and establishes a maximum distance that the subframe may descend in actual use. Spring 44 is amply strong to pull the roller 33 up to the roller 36. Master cylinders have slot openings to house master clamps, but the form roller 33 will be supported by the spring and will not have a ten dency to drop into the slot.

A set of rollers 50 provide for fountain roll and metering functions to bring up a film of moisture from a fountain and make that moisture accessible to the acceptor roll 39.

In operation, the subframe 29 is moved to position the form roller 33 against the surface of a master on the cylinder and to position the acceptor roller 39 in contact with the fountain roll system 50. The speed of surface rotation of the form roller 33 is caused, by reason of friction losses in the system, to be less than the surface speed of the cylinder, but in the same direction. In this manner, a gentle rubbing action is achieved to simulate the former hand preparation of masters and to assure complete wetting of all background surfaces.

Before a master is installed, the subframe 29 is blocked in an operative condition by a pair of blocks 52 operating under each end of the shaft of the intermediate roller 36. One of the blocks 52 is seen best in FIG. 7, although in phantom outline. Only one block will be referred to in the description hereafter. The physical form of the block 52 is shown in FIG. 2 in exploded relationship to its operative position.

A position arm 54 is interlocked with the block 52 by means of a tongue and groove interconnection which permits relative rotational movement about two opposed centers. Arm 54 is centered about a shaft 56 which extends across the frame 13. Block 52 is pivoted on center 57. Shaft 56 is also provided with a rocker arm 58 which is spring loaded by a spring 59 urging the shaft in a clockwise rotational direction. The spring therefore urges the position arm 54 to force the block 52 about center 57 toward a position under the shaft of intermediate roller 36.

An electrical solenoid 61 connects through an arm 63 to rocker arm 58 for driving the shaft 56 and the position arm 54 against the urge of spring 59. When the solenoid 61 is operated, the block 52 is driven to a nonblocking retracted position which allows the subframe 29 and the three rollers carried thereby to fall downwardly against the surface of the master cylinder to the extreme position permitted by the hook 46.

Because the operative parts are many in number, and superposed in front of one another, no one illustration in the drawings is complete with all of the parts to which reference has been made. FIG. 1 brings forth only the rollers 33, 36 and 39 and the book 46. FIG. 2 has eliminated all of the frame 13 and the various controls normally associated with the operation of the subframe 29. Likewise, in FIG. 7, the presence of the three rollers has been subordinated and hook 46 eliminated.

Therefore, to better understand the operation of the manipulation subframe 29, schematic sketches have been shown in FIGS. 8 and 9. The block 52 is shown in full lines in FIG. 8 in its blocking position, and both the positioning arm 54 and the block 52 are shown in phantom outline in the position to which it is actuated by the solenoid. The full line drawing of block 52 shows the surface of the block in supporting contact under the full line position of the shaft of intermediate roller 36. The phantom outline of the shaft of intermediate roller 36 is shown in contact with the edge of the block 52 in the downward position of the roller.

The movement of the set of rollers is exaggerated in all views. The actual amount of movement is in the nature of the thickness of a few sheets of paper, being sufficient to allow the form roller 33 to clear the surface of the master, and little more. Nevertheless, the exaggerated illustration indicates that the block 52 will permit the shaft of the intermediate roller 36 to drop and then the block 52 cannot return under the urge of the spring 59 after the solenoid 61 releases the drive force supplied. The springis not sufficiently strong to drive block 52 to actually elevate the series of rollers and the subframe 29.

The entire operating cycle of the lithographic machine is controlled in proper sequence by electrical circuitry and power devices in the known manner, for example as shown in US. Pat. No. 3,056,346. By this invention; the hand operated plate-etch is replaced by the sequentially timed applicator herein described.

The specific circuit is substantially self-evident from an inspection of FIGS. 10 and 11. FIG. 11 is diagrammatic, and represents the circuits to control such typical operations as counting of printed output, ejection of spent masters, blanket cleaning, and indicator signals. It includes a variable resistor 64.

In FIG. 10, a set of contacts C, of a relay operated by the circuit control provides a momentary closed circuit across the illustrated power lines. The closed circuit includes a rectifier, and a resistor-condenser circuit, with resistor 64 as one element thereof. This circuit serves the purpose of multiplying the time of the effectiveness of the pulse through contacts C, upon relay R.

Relay R has contacts C in a separate circuit which includes the solenoid 61. Therefore, when contacts C close, solenoid 61 is activated, and continues to operate until the resistor-condenser circuit decays.

The decay of the circuit, to release relay R, then activates other contacts, not shown, to rock the frame 13 and end the premoistening cycle.

The timing of sequences is such that the form roller 33 is brought into contact with the cylinder 11 prior to insertion of a new master, in order that the cylinder surface will cause the tail end of the master to adhere to the cylinder surface.

The form roller 33 will contact the cylinder and remain in contact with the surface until physically elevated. During this period of contact of the form roller 33 with the master, FIG. 8 indicates that the acceptor roll 39 is in contact with the fountain roll 50. Moisture is then supplied through a continuous train without depletion.

After the electrical control circuit has determined a preselected period of time, the cam 21 is actuated to bring the high portion of the cam in contact with the cam follower 20 and force the frame 13 to pivot the form roller 14 down into contact with the master on the cylinder 11. Such downward movement of the main frame 13 would normally cause the form roller 33 to move around the surface of the cylinder 11 without lifting. However, it is necessary when the form roller 14 becomes active, to raise the form roller 33 to an inactive condition.

For that purpose, a cam 65 is secured to the frame 10 under the shaft of the intermediate roller 36. The shaft is not in contact with the upper surface of cam 65 during the time the subframe is blocked by the block 52, and although FIG. 9 shows the shaft substantially in contact with the cam 65 in FIG. 9, there is actually provided a very small clearance in order to avoid any necessity for extreme precision in cam placement.

The cam 65 has an upwardly extending forward end portion 66, the upper surface of which extends somewhat radially of the cylinder 11. Placement of this upwardly extending surface just under the shaft of the intermediate roller 36 will cause the shaft of the intermediate roller 36 to climb up that end surface 66 whenever the frame 13 is lowered. Such upward climbing will move the subframe 29 away from the center of the cylinder 11 and thus force a separation of the form roller 33 from the cylinder surface.

To make the movements more understandable, centerlines have been included in FIGS. 8 and 9. In FIG. 8 the frame 13 is elevated and a centerline is drawn between the main frame pivot 17 and the subframe pivot 31. Whenever the solenoid 61 allows subframe 30 to pivot downwardly, a slight movement takes place as shown by the double centerline between the pivot 31 and the center of the shaft on intermediate roller 36. The full lines indicate the neutral condition, and the dotted lines indicate the active surface wetting condition in FIG. 8.

In FIG. 9, the full lines indicate the position of the frame 13 and the fountain solution series roller 14 in the lowered, active condition. The dotted outline indicates the former retracted condition. From a comparison of the angle X in FIG. 8 with the angle Y in FIG. 9 it will be seen that the angle Y is larger, indicating a flattening of the angle relationship between the two frames, which results in forcing the shaft of roller 36 to climb the cam end 66 and thereby lift the form roller 33 from the master cylinder 11, and roll 39 from fountain rolls 50.

Then, having elevated the subframe 29 and the shaft of roller 36, with respect to frame 13, the block 52 is able to move back into blocking position as illustrated in FIG. 9.

Because the acceptor roll 39 moves out of contact with the fountain rollers 50 during the inactive condition, separate power must be supplied to the fountain rollers of assembly 50 if the surface thereof is to be in constant preparation for supplying the moisture when called upon. This invention also provides for this contingency by the series of drives illustrated best in FIG. 5.

Because of space limitations, power from the main machine power source is supplied to the pivot shaft 31 and through a gear train culminating in a gear 68 connected to the shaft of intermediate roller 36. The opposite end of roller 36 is then fitted with a gear 70 and the fountain roller is fitted with a driven gear 72.

Intermediate the gears 70 and 72, is a unique transmission gear structure 74. See FIG. 6. Structure 74 comprises a hub 76 with an elongated slot 78 in which a flattened end of shaft 80 resides. Shaft 80 is a shaft for the acceptor roller 39. A rim gear 82 is slidably fitted to the outside diameter of the hub 76 and is free to drive independently of the hub 76. Therefore, drive from the gear 70 is transmitted through the rim gear 82 to the fountain gear 72 without necessity of rotation of the acceptor roller 39.

Acceptor roller 39 is driven by surface contact with the intermediate roller 36. The roller 39 is mounted in the subframe 39, and therefore pivots with that frame into-and-out-of contact with the surface of the fountain roller, and maintains the straight line relationship of the three roller shafts at all times. However, the hub 76 is urged toward the fountain roller at all times by means of a leaf spring 84 which is clipped under two pins 86 carried by the hub, and over the shaft 80.

The roller 39 will move away from the fountain, and will drive continuously, and the fountain will also remain in constant drive contact.

We claim:

1. In combination, a lithographic printing machine having a master plate cylinder and a system for the sequential application of different moisture treatment to said cylinder, comprising:

a frame, a first form roller carried by said frame, means to supply moisture to said first form roller, and means for moving said frame between a retracted position wherein said first form roller is removed from said cylinder, and a service position wherein said first form roller is in contact with said cylinder;

a subframe, a second form roller carried by said subframe, means to supply moisture to said second form roller, said subframe having a service position wherein said second form roller is in contact with said cylinder, and a retracted position;

means for affecting movement of said subframe to place said second form roller in said service position; and

means responsive to movement of said frame to said service position for shifting said subframe to said retracted position.

2. The combination as defined in claim 8 wherein said frame and subframe are articulated with a pivot interconnection between the frames at a mean position, and the frames extending to extremes;

a fixed position pivot connecting the extremes of said first frame to said machine;

a guide cam track for said subframe carried in fixed relationship to said machine and establishing a path divergent from said cylinder;

means for moving said pivot interconnection between a first position of maximum elevation with the angular relationship of the frames placing the form roll of said subframe in said service position, and a second position of greater angular relationship with the subframe riding said cam track to said retracted position.

3. The combination as defined in claim 1 in which there is also provided;

a withdrawable support member coacting with the subframe for preventing contact of its form roll with the cylinder when the first angular relationship is first resumed; and

control means for withdrawing the support member to permit normal contact of the subframe form roll with the cylinder when desired.

4. The combination as defined by claim 1, wherein said means to supply moisture to said second form roller comprises:

two sideplates of said subframe;

an intermediate roller carried on said side plates by bearings;

an upwardly opening bottom slot in each side plate, said form roller having a shaft with end portions residing in said slots;

a downwardly opening top slot in each side plate;

an acceptor roller with shaft ends residing in said top slots;

resilient means urging said form roller and said acceptor roller into said slots and into surface alignment with said intermediate roller;

whereby, said system of the subframe is self-alignable to the master cylinder and to one another when the subframe rests on the cylinder gravity contact.

5. A master conversion system in combination with a lithographic printing machine having a master cylinder, comprising'.

a main frame having supply rolls with a form roll for rolling contact with said master cylinder;

a pivot mounting for said main frame located a distance from said form roll, said form roll on said frame swingable about said pivot mounting between a first position retracted from said master cylinder and a second position against said cylinder;

a subframe having supply rolls with a form roll for rolling contact with said master cylinder;

said main frame and subframe articulated by a pivot interconnection located a distance from said pivot mounting of said main frame, said pivot interconnection is swingable through an arc corresponding to that of said form roll of the main frame;

a diverting cam adjacent said subframe;

said subframe having a cam follower surface positioned to ride said diverting cam, said subframe normally extending from the pivot interconnection to a first position relative to said cylinder wherein its form roll is in rolling contact with said cylinder when the frames are held in a first angular relationship, and being extendible to drive said cam follower along said cam to a second position wherein its from roll is spaced from said cylinder as a result of engaging said diverting cam and increasing the angular relationship of said frames to drive the form roll of the subframc farther from said pivot mounting.

6. In combination, a lithographic printing machine having a master plate cylinder and a system for the sequential application of different moisture treatment to said cylinder, compris- 10 ing:

a frame, a first form roller carried by said frame, means to supply moisture to said first form roller, and means for moving said frame between a retracted position wherein said first form roller is removed form said cylinder, and a service position wherein said first form roller is in contact with said cylinder;

means for shifting the frame between at least one of said positions and the other;

a subframe, a second form roller carried by said subframe,

means to supply moisture to said second form roller, said subframe having a service position wherein said second form roller is in contact with said cylinder, and a retracted position and being gravity urged to said service position;

means powered solely by movement of said frame to said service position for shifting said subframe to said retracted position;

means active when said frame is returned to its retracted position normally to permit gravity return of said subframe to service position; and

withdrawable support member preventing such gravity return of said subframe to active position until said support means is withdrawn.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,60 l,3 l9 Dated ptember 1 197 Inventor(s) Arthur W. Sejeck et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column line 2, "phantom" should read dotted Column 6,

line H7, "8" should read l Signed and sealed this 7th day of March 1972.

(SEAL) Attest:

EDWARD M.FLhiTCHER,JR. ROBERT GOTISCHALK Attesting Officer Commissioner of Patents RM PO-IOSO (10-69) a u s sovznwmzm' PRINTING OFHCE Iss9 0-366-334 

1. In combination, a lithographic printing machine having a master plate cylinder and a system for the sequential application of different moisture treatment to said cylinder, comprising: a frame, a first form roller carried by said frame, means to supply moisture to said first form roller, and means for moving said frame between a retracted position wherein said first form roller is removed from said cylinder, and a service position wherein said first form roller is in contact with said cylinder; a subframe, a second form roller carried by said subframe, means to supply moisture to said second form roller, said subframe having a service position wherein said second form roller is in contact with said cylinder, and a retracted poSition; means for affecting movement of said subframe to place said second form roller in said service position; and means responsive to movement of said frame to said service position for shifting said subframe to said retracted position.
 2. The combination as defined in claim 8 wherein said frame and subframe are articulated with a pivot interconnection between the frames at a mean position, and the frames extending to extremes; a fixed position pivot connecting the extremes of said first frame to said machine; a guide cam track for said subframe carried in fixed relationship to said machine and establishing a path divergent from said cylinder; means for moving said pivot interconnection between a first position of maximum elevation with the angular relationship of the frames placing the form roll of said subframe in said service position, and a second position of greater angular relationship with the subframe riding said cam track to said retracted position.
 3. The combination as defined in claim 1 in which there is also provided; a withdrawable support member coacting with the subframe for preventing contact of its form roll with the cylinder when the first angular relationship is first resumed; and control means for withdrawing the support member to permit normal contact of the subframe form roll with the cylinder when desired.
 4. The combination as defined by claim 1, wherein said means to supply moisture to said second form roller comprises: two sideplates of said subframe; an intermediate roller carried on said side plates by bearings; an upwardly opening bottom slot in each side plate, said form roller having a shaft with end portions residing in said slots; a downwardly opening top slot in each side plate; an acceptor roller with shaft ends residing in said top slots; resilient means urging said form roller and said acceptor roller into said slots and into surface alignment with said intermediate roller; whereby, said system of the subframe is self-alignable to the master cylinder and to one another when the subframe rests on the cylinder gravity contact.
 5. A master conversion system in combination with a lithographic printing machine having a master cylinder, comprising: a main frame having supply rolls with a form roll for rolling contact with said master cylinder; a pivot mounting for said main frame located a distance from said form roll, said form roll on said frame swingable about said pivot mounting between a first position retracted from said master cylinder and a second position against said cylinder; a subframe having supply rolls with a form roll for rolling contact with said master cylinder; said main frame and subframe articulated by a pivot interconnection located a distance from said pivot mounting of said main frame, said pivot interconnection is swingable through an arc corresponding to that of said form roll of the main frame; a diverting cam adjacent said subframe; said subframe having a cam follower surface positioned to ride said diverting cam, said subframe normally extending from the pivot interconnection to a first position relative to said cylinder wherein its form roll is in rolling contact with said cylinder when the frames are held in a first angular relationship, and being extendible to drive said cam follower along said cam to a second position wherein its from roll is spaced from said cylinder as a result of engaging said diverting cam and increasing the angular relationship of said frames to drive the form roll of the subframe farther from said pivot mounting.
 6. In combination, a lithographic printing machine having a master plate cylinder and a system for the sequential application of different moisture treatment to said cylinder, comprising: a frame, a first form roller carried by said frame, means to supply moisture to said first form roller, and means for moving said frame between a retracted position wHerein said first form roller is removed form said cylinder, and a service position wherein said first form roller is in contact with said cylinder; means for shifting the frame between at least one of said positions and the other; a subframe, a second form roller carried by said subframe, means to supply moisture to said second form roller, said subframe having a service position wherein said second form roller is in contact with said cylinder, and a retracted position and being gravity urged to said service position; means powered solely by movement of said frame to said service position for shifting said subframe to said retracted position; means active when said frame is returned to its retracted position normally to permit gravity return of said subframe to service position; and withdrawable support member preventing such gravity return of said subframe to active position until said support means is withdrawn. 